Design And Control Of Intelligent Finger Driving System Based On The Shape Memory Alloy

Due to the important practical value,the intelligent bionic hand has been concerned by many researchers at home and aboard.Shape memory alloy(SMA)has been widely used in the actuator field because of its shape memory effect and good mechanical properties.Compared to the traditional driving methods,SMA has the advantages of high power to weight ratio,simple structure,small size,no noise pollution,and with driving and sensing in one,which makes its unique application prospect in micro drive system.However,due to the strong nonlinearity and hysteresis of SMA material,the control accuracy and the driving frequency are low.Therefore,it is very necessary and significant to study the control strategy of intelligent bionic finger based SMA.The main research work of this thesis is as follows:Firstly,the application situation of SMA at home and abroad in the robot hand drive field,and the research status of SMA material control are analyzed.Then a detailed introduction to the shape memory effect,super elasticity,mechanical and resistance properties are given.Secondly,a complete mathematical model of SMA actuator is derived,including a heat conduction model,phase transition model and the dynamic model of the bionic finger.Some experiments have done with the built experimental platform,and some key parameters of the mathematical model are identified.Moreover,the accuracy of the model is verified by comparing the simulation results in MATLAB and experimental results.Then the dynamic analysis of the bionic finger is carried out,which lays the foundation for the next control.Thirdly,based on established mathematical model,the sliding mode control method is studied and compared with PID control method.The sliding mode of SMC can be designed according to the actual system,good control results and robustness can achieve for the nonlinear systems with disturbance and parameter uncertainty.Finally,the designed controller is applied to the drive control system for position tracking control,include step signal and sine signal curve.The corresponding experiments results of PID controller and sliding mode controller are given.Since the nonlinearity and hysteresis of SMA coexist,compared with PID controller,the sliding mode controller can achieve good control effect and make the system track the reference trajectory accurately with small overshoot.